The present invention relates to a recording medium, and more particularly, to a recording medium useful in direct read after write (DRAW) recording arrangements.
One of the problems encountered in recording with a modulated radiation beam, such as a laser or an electron beam, is that a relatively high power radiation beam must be utilized. The power requirements of the laser may be reduced somewhat if a photographic process of recording is used. Unfortunately, this is not the most desirable apparatus, due to the fact that the recording must be completed and the medium must be developed prior to reading the recording. Therefore, any error made during the initial stages of recording may not become apparent until considerable recording and development time has been wasted.
It is far more desirable to use a recording medium that is capable of being read immediately after recording. Such direct read after write recording mediums are generally recorded on by a process that uses a first laser beam to locally affect a surface, such as by forming a pit or a bubble, which changes the local reflection characteristics of the surface. Such change in local reflection characteristics can be immediately detected by a second lower powered laser to read information on the surface, which is written into the surface by way of pit or bubble. The formation of a local area of a sufficient size to be detected by the read laser beam requires a writing laser having substantial radiation power.